Neutralizing superabsorbent polymer composition

ABSTRACT

An absorbent and process for the neutralization and absorption of acidic and alkaline liquid spills comprising a mixture of superabsorbant polymer, a styrene-butadiene-styrene block copolymer, sodium bicarbonate, and optionally a chlorine neutralizer. The absorbent preferably also contains a chlorine neutralizer for the neutralization of any chlorine vapors and a pH indicator to indicate that the spill has been neutralized and is safe for handling and disposal.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention is directed to an absorbent composition and moreparticularly to an absorbent composition that can absorb and neutralizeany type of liquid spill, as well as indicate whether the spill isacidic, basic or neutral by a change in color. The absorbent also treatsvapors, particularly those spills that emit chlorine.

2. Description of Related Art

Most known spill absorbents can absorb many times its weight in water;however, contact with the product after absorption of acid or alkalispills are still hazardous and must be neutralized or disposed ofaccording to pH. Prior techniques show that an acid/basecolor-indicating absorbent will give the user some indication of thepossible hazards associated with the spill. In addition, absorbents thatneutralize both acids and alkalis reduce the danger of making contactwith the product after absorption and eliminate hazardous wastedisposal.

One such product, “Ampho-Mag”™ is an amphoteric buffer comprised ofsulfuric acid, magnesium oxide and/or magnesium hydroxide, and water,available from Premier Chemicals LLC located in King of Prussia Pa. Thissorbent also claims to meet the need for a non-caking, neutralizingamphoteric buffer with good storage properties, as opposed to amagnesia/Epsom salt blend, such as the one sold under the tradename “pH9” by Terra Environmental. However, the use of a buffer that containsmetals can result in unanticipated reactions and many of theseabsorbents must be conditioned in order to provide completeneutralization. Therefore, there is still a need for an improvedneutralizing absorbent.

SUMMARY OF THE INVENTION

The present invention involves an absorbent and a process of using theabsorbent to absorb and neutralize various types of spills and vapors.The absorbent comprises a mixture of a superabsorbant polymer, astyrene-butadiene-styrene block copolymer, and sodium bicarbonate. Theabsorbent preferably also contains a chlorine neutralizer for theneutralization of any chlorine vapors and a pH indicator to indicatethat the spill has been neutralized and is safe for handling anddisposal. Preferably the absorbent further resists hardening and cakingduring storage.

The absorbent can be said to be an efficient and effective neutralizerof both weak and strong acids and alkalis, as well as chlorine vapor.Therefore, it acts as an amphoteric buffer where acid and alkali spillsare safe to handle and dispose of in a regular manner. This allows asingle absorbent composition to be used on a wide variety of liquidspills. Another advantage of the present invention is that the absorbentdoes not require the presence of any metals in the sorbent andpreferably is essentially free of metals. Preferably, the absorbent alsocontains a chlorine-neutralizing compound to allow the absorbent toneutralize chlorine vapors, such as those generated from liquid spillscontaining bleach. The method of using the absorbent involves applying asufficient amount of the novel absorbent to a liquid spill to neutralizeand absorb the spill. An optional pH indicator in the absorbent can beused to determine when the spill has been sufficiently neutralized.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

A preferred embodiment of the current invention can be prepared byadding appropriate amounts of sodium bicarbonate, and astyrene-butadiene-styrene block copolymer to a sodium polyacrylatepolymer. In a more preferred embodiment, an appropriate amount of achlorine neutralizer compound is also added to the other components. Oneor more pH indicator solution(s) are then preferably sprayed on theabsorbent while mixing. The preferred absorbent provides goodabsorbency, indicates pH, neutralizes acids and alkalis, and storeswithout caking. In addition, it is free of metals, easily manufactured,and it does not need conditioning with water for optimum neutralization,as in the prior art. The direct addition of components in the preferredembodiment of the present invention avoids intermediate compounds andreactions where hydration of metal compounds is pertinent for optimumuse, as described in related art.

The high absorption rate of the preferred mixture is due to the additionof a sodium polyacrylate polymer. Without being bound by theory, it iscurrently believed that when hydrated, the carboxyl groups of thepolymer dissociate into negatively charged carboxylate ions (COO⁻¹),which repel one another along the polymer chain. This widening of thepolymer coils allows water to move into the proximity of more carboxylgroups, while maintaining a gel-like consistency from hydrogen bondingbetween the water and the carboxylate ions between chains. Then thespill can easily be picked up with a broom or squeegee and dustpan. Thestyrene-butadiene-styrene block copolymer is included in the absorbentcomposition to increase absorbency when working with oil-based spills.

The neutralizing property for both acids and alkalis makes this mixtureamphoteric. The spill waste becomes safe to handle because the absorbentbrings the pH to a range of 6-8. Sodium bicarbonate is capable ofneutralizing acids by producing a sodium salt, water, and carbondioxide. Reaction (1) is a representative reaction, which may occur whencleaning up a spill of phosphoric acid.3NaHCO₃+H₃PO₄→Na₃PO₄+3H₂O+3CO₂(g)  (1)

The preferred superabsorbant polymer is also capable of neutralizingalkaline solutions as well. Acrylic acid is the monomer from which thepreferred polymer is formed. Reaction (2) is representative of areaction that may occur during clean up of a caustic spill. The polymersreliance on osmotic balance also aids in bringing the spill to a moreneutral pH.C₃H₄O₂+NaOH→NaC₃H₃O₂+H₂O  (2)

This buffering effect produces a neutralized material with a pH veryclose to 7, which is significantly less dangerous than that of theun-neutralized acid or base.

Exposure to chlorine vapors is a big concern, especially with bleachspills. For this reason, a more preferred embodiment of the currentinvention also comprises a chlorine-neutralizing compound. Someneutralizers of this type include sodium sulfite, sodium thiosulfate,and ascorbic acid (or Vitamin C). Reaction (3) represents the reactionthat may occur when applying the buffer to a bleach spill.Na₂SO₃+HOCl→Na₂SO₄+HCl  (3)

The addition of a chlorine neutralizer ensures a safer spill pick-up andavoids exposing the user to trapped chlorine vapors that would otherwisebe released when disturbing the treated spill during clean up.

The addition of at least one pH indicator into the absorbent provides avisual way to confirm whether the spill has been neutralized to a safepH level. The indicator serves as a warning to the user that the spillmay be corrosive, and it should not be touched if there is a colorchange. Spraying the indicator as a water-based solution on thepreferred absorbent while mixing is the best way of obtaining aconsistent mixture. Convenient pH indicators include bromophenol blue,methyl yellow, phenolphthalein, phenol red, and thymolphthalein. Theinvention is not limited to those described: therefore, any indicator orcombination that visually shows pH changes may be used. The amount of pHindicator that should be used in the absorbent is determined by thecolor intensity that is desired.

An attractive feature of the preferred absorbent is that it is free ofmetals and does not require precise hydration of the product, as inprior art. The preferred absorbent is also able to absorb over fortytimes its weight in water. Therefore, even in humid conditions theproduct remains free flowing. Furthermore, the preferred absorbent canbe manufactured using all solid components, with exception of theindicator(s) solution, making it possible to control manufacture of thefinal material in an economical and efficient manner. Also, thecombination of components in the preferred absorbent lessens heatformation during spill clean up of all solutions, even more so than“Ampho-Mag”™. The ease of manufacture of the preferred absorbenteliminates undesirable caking and/or hardening during storage orapplication, and does so without excessive heat generation or theconcern of conditioning the absorbent for complete neutralization. Oncethe product maintains its original color after completely covering thespill, it is considered neutralized.

The preferred method of production of the most preferred embodiment isthe combination of superabsorbant polymer, a styrene-butadiene-styreneblock copolymer, sodium bicarbonate, and a chlorine-neutralizingcompound in a suitable mixer such as a ribbon mixer. The material ispreferably processed batch wise. A preferred embodiment of the presentinvention is formed from components comprising by weight percent:superabsorbant polymer 25-60%, most preferably about 45%;styrene-butadiene-styrene block copolymer 20-35%, most preferably about30%; sodium bicarbonate 10-50%, most preferably about 15%; chlorineneutralizing compound 5-20%, most preferably about 10%. The process aimsto produce a product where the weight ratio of the above components isapproximately 4.5:3.0:1.5:1.0, respectively. All of the components canbe added to the mixer simultaneously before mixing. Once mixing hascommenced, the pH indicator(s) can be sprayed into the mixture throughthe use of a suitable pump-up sprayer, such as a Hudson sprayer with amedium spray setting. Sizing of the resultant particles of the productshould not be necessary. The raw materials are large enough to avoiddusting, but small enough to permit rapid reaction with the spill.

EXAMPLE 1

Content Analysis for Metals

A sample of a preferred embodiment of the present invention containingthe most preferred weight ratio of superabsorbant polymer, astyrene-butadiene-styrene block copolymer, sodium bicarbonate, and achlorine-neutralizing compound was analyzed using the EPA 6000/7000Series Metals method. The results confirmed that the product is indeedfree of metals, unlike “Ampho-Mag”™, which is magnesium-based.

EXAMPLE 2

Analysis for Off-gassing of Chlorine Gas

The waste of a bleach spill treated with the absorbent prepared inExample 1 was analyzed for emission of chlorine gas using chlorine teststrips. The color of the strip remained unchanged, even after disturbingthe treated spill, indicating that the chlorine had been neutralized.Similarly, the same test was performed with the “Ampho-Mag” ™ absorbent.The chlorine test strip did not change color initially, but afterdisturbing the treated spill to clean it up, the strip changed colorslightly, indicating the presence of about 10 ppm chlorine.

EXAMPLE 3

Product Storage Handling Testing

A sample of the absorbent prepared in Example 1 was checked for itsability to resist “caking” under hot storage conditions. Duplicatesamples were heated in a sealed vial in a convection oven at 120 degreesF. The samples were probed on a regular basis to check for “cake”formation. Neither sample showed any signs of hardening after 30 days at120 degrees F.

EXAMPLE 4

Neutralization Testing

The following preparations were carried out by mixing all theingredients simultaneously in a ribbon mixer. Table 1 describes thechemical composition of Absorbents #1-4. TABLE 1 Absorbent AbsorbentAbsorbent Absorbent #1 #2 #3 #4 Superabsorbant Polymer 25% wt 45% wt 35%wt 50% wt Block Copolymer 20% wt 30% wt 25% wt 25% wt Sodium Bicarbonate50% wt 15% wt 25% wt 20% wt Chlorine Neutralizer  5% wt 10% wt 15% wt 5% wt

The ability of Absorbents #1-4 as well as “Ampho-Mag”™ absorbent toneutralize both acids and alkalis was evaluated by reacting each with75% phosphoric acid or 50% caustic until neutralization was complete.The final pH was checked by wetting a spot of the treated spill withdeionized water enough to use a pH paper strip. All of the formulationswere capable of neutralizing both spills when the formulations wereapplied in excess of the stoichiometric quantity required forneutralization. These findings were also confirmed by using EPA method9045C on a number of products that can be found in a grocery store. Evenspill products with an original pH less than 0 or greater than 12 had apH of 6-8 after treatment with the absorbents.

EXAMPLE 5

Heat Generation of Superabsorant Polymer-based Absorbents #1-4

The reactions of Absorbents #1-4 generated considerably less heat than“Ampho-Mag”™ absorbent, as shown in Table 2. This analysis was performedwith a Raytek infrared noncontact thermometer in conjunction with theprocedure described in Example 4. The heat that was generated dissipatedin a matter of minutes for Buffers #1-4, where as the heat generated by“Ampho-Mag”™ absorbent took considerably longer to reach roomtemperature. TABLE 2 Absorbent Absorbent Absorbent Absorbent “Ampho- #1#2 #3 #4 Mag” ™ Temperature w/ Room 77 75 78 95 H₂O Temperature (degreesF.) Temperature w/ Room Room Room Room 130 75% H₃PO₄ TemperatureTemperature Temperature Temperature (degrees F.) Temperature w/ 100 9096 92 141 50% NaOH (degrees F.) Temperature w/ 93 101 107 93 91 bleach(degrees F.)Note:Room temperature is 72 degree F.

The above descriptions of certain embodiments are made for the purposesof illustration only and are not intended to be limiting in any manner.Other alterations and modifications of the preferred embodiment willbecome apparent to those of ordinary skill in the art upon reading thisdisclosure, and it is intended that the scope of the invention disclosedherein be limited only by the broadest interpretation of the appendedclaims to which the inventor is legally entitled.

1. An absorbent for the neutralization and absorption of liquid spillscomprising: a superabsorbent polymer; styrene-butadiene-styrene blockco-polymer; and sodium bicarbonate.
 2. The absorbent of claim 1 furthercomprising a pH indicator.
 3. The absorbent of claim 1 wherein thesuperabsorbent is present in an amount of from about 20 to about 60 wt.% and the sodium bicarbonate is present in an amount of from about 10 toabout 50 wt. % sodium bicarbonate.
 4. The absorbent of claim 3 whereinthe superabsorbent is present in an amount of about 45 wt. % and thebicarbonate is present in an amount of about 15 wt. %.
 5. The absorbentof claim 1 wherein the absorbent is essentially free of metals.
 6. Theabsorbent of claim 1 wherein the superabsorbent polymer is a bindingpolyacrylate polymer.
 7. The absorbent of claim 6 wherein thesuperabsorbent polymer is sodium polyacrylate polymer.
 8. The absorbentof claim 1 wherein the absorbent is cake resistant.
 9. The absorbent ofclaim 1 wherein the absorbent is capable of neutralizing both acidic andalkaline spills.
 10. The absorbent of claim 1 further comprising achlorine neutralizing compound.
 11. The absorbent of claim 10 whereinthe chlorine neutralizing compound is selected from the group consistingof, sodium thiosulfate, sodium sulfite, ascorbic acid, and mixturesthereof.
 12. The absorbent of claim 10 wherein the superabsorbentpolymer is a binding polyacrylate.
 13. The absorbent of claim 10 whereinthe chlorine neutralizing compound is present in an amount of from about5 to about 20 weight percent.
 14. The absorbent of claim 13 wherein thechlorine neutralizing compound is present in an amount of about 10weight percent.
 15. The neutralizing absorbent of claim 10 wherein theabsorbent contains from about 25 to about 60 weight percentsuperabsorbant, from about 20 to about 35 weight percent blockcopolymer, from about 10 to about 50 weight percent sodium bicarbonate,and from about 5 to about 20 weight percent chlorine neutralizer. 16.The neutralizing absorbent of claim 15 wherein the absorbent containsabout 45 weight percent superabsorbant, about 30 weight percent blockcopolymer, about 15 weight percent sodium bicarbonate, and about 10weight percent chlorine neutralizer.
 17. The absorbent of claim 10wherein the absorbent is essentially free of metals.
 18. The absorbentof claim 17 wherein the absorbent is completely free of metals.
 19. Theabsorbent of claim 10 further comprising a pH indicator.
 20. Theabsorbent of claim 19 wherein the pH indicator is selected form thegroup consisting of bromophenol blue, methyl yellow, phenolphthalein,phenol red, thymolphthalein, and mixtures thereof.
 21. The absorbent ofclaim 10 further comprising a pH indicator and wherein thesuperabsorbent polymer is sodium polyacrylate polymer, the chlorineneutralizing compound is selected from the group consisting of, sodiumthiosulfate, sodium sulfite, ascorbic acid, and mixtures thereof, andwherein the absorbent is essentially free of all metals, and wherein theabsorbent contains from about 25 to about 60 weight percentsuperabsorbant, from about 20 to about 35 weight percent blockcopolymer, from about 10 to about 50 weight percent sodium bicarbonate,and from about 5 to about 20 weight percent chlorine neutralizer. 22.The neutralizing absorbent of claim 15 wherein the absorbent containsabout 45 weight percent superabsorbant, about 30 weight percent blockcopolymer, about 15 weight percent sodium bicarbonate, and about 10weight percent chlorine neutralizer.
 23. The absorbent of claim 21wherein the absorbent is cake resistant.
 24. A process for neutralizingand absorbing an acidic or alkaline liquid spill comprising the stepsof: identifying a liquid spill; applying a sufficient quantity of anabsorbent comprising, a superabsorbant polymer, astyrene-butadiene-styrene block copolymer, and sodium bicarbonate toneutralize and absorb the liquid spill.
 25. The process of claim 24wherein the absorbent further comprises a pH indicator.
 26. The processof claim 24 wherein the superabsorbent is present in the absorbent in anamount of from about 20 to about 60 wt. % and the sodium bicarbonate ispresent in an amount of from about 10 to about 50 wt. % sodiumbicarbonate.
 27. The process of claim 26 wherein the superabsorbent ispresent in the absorbent in an amount of about 45 wt. % and thebicarbonate is present in an amount of about 15 wt. %.
 28. The processof claim 24 wherein the absorbent is essentially free of metals.
 29. Theprocess of claim 24 wherein the superabsorbent polymer is a bindingpolyacrylate.
 30. The process of claim 29 wherein the superabsorbentpolymer is sodium polyacrylate polymer.
 31. The process of claim 24wherein the absorbent is cake resistant.
 32. The process of claim 24wherein the absorbent is not conditioned prior to being applied to thespill.
 33. The process of claim 24 wherein the absorbent furthercomprises a chlorine neutralizing compound.
 34. The process of claim 33wherein the chlorine neutralizing compound is selected from the groupconsisting of, sodium thiosulfate, sodium sulfite, ascorbic acid, andmixtures thereof.
 35. The process of claim 33 wherein the superabsorbentpolymer is a binding polyacrylate.
 36. The process of claim 33 whereinthe chlorine neutralizing compound is present in the absorbent in anamount of from about 5 to about 20 weight percent.
 37. The process ofclaim 36 wherein the chlorine neutralizing compound is present in theabsorbent in an amount of about 10 weight percent.
 38. The neutralizingabsorbent of claim 33 wherein the absorbent contains from about 25 toabout 60 weight percent superabsorbant, from about 20 to about 35 weightpercent block copolymer, from about 10 to about 50 weight percent sodiumbicarbonate, and from about 5 to about 20 weight percent chlorineneutralizer.
 39. The neutralizing absorbent of claim 38 wherein theabsorbent contains about 45 weight percent superabsorbant, about 30weight percent block copolymer, about 15 weight percent sodiumbicarbonate, and about 10 weight percent chlorine neutralizer.
 40. Theprocess of claim 33 wherein the absorbent is essentially free of metals.41. The process of claim 40 wherein the absorbent is completely free ofmetals.
 42. The process of claim 33 wherein the absorbent furthercomprises a pH indicator.
 43. The process of claim 42 wherein the pHindicator is selected form the group consisting of bromophenol blue,methyl yellow, phenolphthalein, phenol red, thymolphthalein, andmixtures thereof.
 44. The process of claim 33 wherein the absorbent isnot conditioned prior to being applied to the spill.
 45. The process ofclaim 33 wherein the absorbent further comprises a pH indicator andwherein the superabsorbent polymer is sodium polyacrylate polymer, thechlorine neutralizing compound is selected from the group consisting of,sodium thiosulfate, sodium sulfite, ascorbic acid, and mixtures thereof,the absorbent is essentially free of all metals, the absorbent containsfrom about 25 to about 60 weight percent superabsorbant, from about 20to about 35 weight percent block copolymer, from about 10 to about 50weight percent sodium bicarbonate, and from about 5 to about 20 weightpercent chlorine neutralizer, and wherein the absorbent is notconditioned prior to being applied to the spill.
 46. The neutralizingabsorbent of claim 45 wherein the absorbent contains about 45 weightpercent superabsorbant, about 30 weight percent block copolymer, about15 weight percent sodium bicarbonate, and about 10 weight percentchlorine neutralizer.
 47. The process of claim 45 wherein the absorbentis cake resistant.